What steps will reproduce the problem?
1. start fishinh (or any other channelled spell)
2. select yourself as target
3. deselect target (so you don't have anything in target)

What is the expected output? What do you see instead?
I expcet to see the target's casting bar after step #2 and I expect the target's casting bar to disappear when deselecting/losing my target in step #3.

The target's casting bar is displayed until the end of channelling time although there is no target anymore

This of course not only when targeting oneself but always when you deselect your target or select a target you specified "don't display casting bar" after target started channelling a spell

What version of the product are you using?
r010

Do you have an error log of what happened?
no error log

Please provide any additional information below.

if not UnitExists('target') then
        return
    end
    if not db.profile.showfriendly then
        if UnitIsFriend('player', 'target') then
            return
        end
    end
    if not db.profile.showhostile then
        if UnitIsEnemy('player', 'target') then
            return
        end
    end

should be changed to:
if not UnitExists('target') then
        castBarParent:Hide()
        return
    end
    if not db.profile.showfriendly then
        if UnitIsFriend('player', 'target') then
            castBarParent:Hide()
            return
        end
    end
    if not db.profile.showhostile then
        if UnitIsEnemy('player', 'target') then
            castBarParent:Hide()
            return
        end
    end

code example is from function QuartzTarget:PLAYER_TARGET_CHANGED()in file Quartz_Target.lua affects Quartz_Focus also